From textbook: 'the most common sources of stem cells are bone marrow and the placenta. However, scientists have recently found precursor cells in the pancreas of adult mice. These cells are capable of developing into a variety of cell types and may be true stem cells. If similar cells can be found in the human pancreas then they could be used to produce new B cells in patients with type 1 diabetes'.

What does this passage mean? What do they mean by 'true stem cells'? Also what are precursor cells?

(Original post by tazmaniac97)
From textbook: 'the most common sources of stem cells are bone marrow and the placenta. However, scientists have recently found precursor cells in the pancreas of adult mice. These cells are capable of developing into a variety of cell types and may be true stem cells. If similar cells can be found in the human pancreas then they could be used to produce new B cells in patients with type 1 diabetes'.

What does this passage mean? What do they mean by 'true stem cells'? Also what are precursor cells?

Stem cells are cells which can divide a practically unlimited number of times. There are different kinds of stem cells. Some stem cells, such as ones found in really early embryos, can give rise to ANY cell type in the body, given the right stimulus. Others, like haematopoetic stem cells in the bone marrow, can give rise to several different cell types (in this case, all the different cell types found in your blood), but not absolutely any cell type (so these blood stem cells couldn't give rise to muscle cells, or skin cells etc). Precursor cells are cells which give rise to one or a few specific cell types (e.g. lymphoblasts may give rise to T lymphocytes or B lymphocytes) but a precursor cell may or may not be a stem cell, and therefore may or may not be limited in the number of times it can divide.

The paragraph means that in mice, cells have been found which can turn into several different types of pancreatic cell. If these discovered cells are found to be true stem cells, which could divide an unlimited number of times, they could be used to make as many pancreatic cells as you wanted. The presence of such cells in mice make it a plausible idea that the human pancreas might contain pancreatic stem cells. If human pancreatic stem cells exist, they could be used to make human pancreatic cells to replace missing beta cells in patients with type 1 diabetes.

(Original post by schtim)
Stem cells are cells which can divide a practically unlimited number of times. There are different kinds of stem cells. Some stem cells, such as ones found in really early embryos, can give rise to ANY cell type in the body, given the right stimulus. Others, like haematopoetic stem cells in the bone marrow, can give rise to several different cell types (in this case, all the different cell types found in your blood), but not absolutely any cell type (so these blood stem cells couldn't give rise to muscle cells, or skin cells etc). Precursor cells are cells which give rise to one or a few specific cell types (e.g. lymphoblasts may give rise to T lymphocytes or B lymphocytes) but a precursor cell may or may not be a stem cell, and therefore may or may not be limited in the number of times it can divide.

The paragraph means that in mice, cells have been found which can turn into several different types of pancreatic cell. If these discovered cells are found to be true stem cells, which could divide an unlimited number of times, they could be used to make as many pancreatic cells as you wanted. The presence of such cells in mice make it a plausible idea that the human pancreas might contain pancreatic stem cells. If human pancreatic stem cells exist, they could be used to make human pancreatic cells to replace missing beta cells in patients with type 1 diabetes.

Oh I understand now, thanks

One more question: why can stem cells divide an unlimited amount of times, whilst other body cells can't?

One more question: why can stem cells divide an unlimited amount of times, whilst other body cells can't?

On each end of each chromosome is a protective cap, made of folded up DNA, called a telomere. When a cell divides, its telomeres get a little bit shorter. There comes a point in most cells where the telomeres become so short that the cell "decides" to stop dividing-this helps stop cancers forming, because old cells are more likely to have damaged DNA. Stem cells, however, have an enzyme called telomerase which can lengthen telomeres again after each cell division.